When a photographic representation of a three-dimensional object is formed on a two-dimensional surface, it often takes on an unnatural quality. The image appears overly sharp and details that are not readily apparent when an object is viewed with the naked eye are exaggerated. This effect is particularly noticable and objectionable in portraiture since facial lines and blemishes tend to be too pronounced and sharply defined.
It has been theorized that the unnatural appearance of an overly shape image is attributable to the absence of the stereoscopic that is present when objects are viewed normally. This effect has a tendency to round corners and soften lines of demarkation.
The master painters recognized this problem centuries ago and developed a technique for softening lines to give depth to their work. Photographers have sought, with only limited success, to achieve the same result.
The most common photographic techniques for softening an image, giving it some increased depth and realism, is the use of a diffusion filter. In essence, a diffusion filter is simply a transparent glass or plastic plate that has a roughened surface. It is placed between the photographic subject and the image forming lens. Most of the light reflected by the subject passes through the filter. Some of the light, however, is diffused by irregularities on the surface of the filter and softens the image.
It has been found that conventional diffusion filters have marked disadvantages, primarily halation and veiling. Halation is the tendency of bright areas of the image to be surrounded by a "halo" of diffused light. This effect can be surprisingly pronounced and is highly objectionable if not controlled. For example, a portrait of a person with light hair against a black background will show a lightened area surrounding the hair and extending far into the background. As the amount of diffusion increases, the size and intensity of the halo increases.
"Veiling" refers to the tendency of diffused light to impinge upon all areas of the image format, giving the impression of a whitish veil covering the entire image. Most noticable is the loss of the true black which takes on a distinctly grayish tone. Veiling and haloing are attributable to heterogeneous light, i.e., light that is collected by the lens but is disorganized and is not capable of being focused to form an image.
The principle objective of the invention is to provide an improved diffusion filter that significantly reduces both haloing and veiling.